I know this may dash one's ego and brilliance, however maybe you could conform the waterfill entity behavior like all other entities in the game. Pretty abstract right? Each entity in the game, all the objects you place on the map... yes those, when you place one top of you by accident, there is message, that says, "PLAYER IN THEY WAY" or something like that. The entity won't kill you. What do you think? Too hard right?